Bicycles have long been used as a means of transportation and recreation. However, virtually all bicycles known in the prior art have involved a relatively rigid frame, which transmits directly to the rider shocks resulting from potholes, rocks, or other unevenness in the riding surface. This has resulted in discomfort to the rider which is at the least undesirable, if not unacceptable.
The solution to this problem found in the prior art has been to include a shock absorbing suspension on the bicycle similar to those found in motorcycles or on cars. Thus, for example, British Patent No. 104,022 discloses a suspension arrangement for motorcycles, cycles and the like in which a shock absorber is mounted on an extra seat riser tube and is connected via a linkage to the rear wheel and its associated control arms.
Likewise, French Patent No. 933,079 discloses a somewhat similar arrangement which involves two shock absorbers but only a single seat riser tube. Yet another example is found in U.S. Pat. No. 944,795, which again is intended for use in "motorcycles, bicycles and the like" and involves a single shock absorber mounted behind the seat riser tube and connected there to the control arms for the rear wheel. Yet another example is found in U.S. Pat. No. 978,881, intended for use in motorcycles and the like, in which a shock absorbing means is positioned along the upper backstays, or swing arms, with the amount of travel limited by backstays connected near the tip of the rear fork.
Yet another example is shown in U.S. Pat. No. 1,039,684, described as a shock absorber for motor cycles, in which a shock absorber is located immediately behind the seat riser and connected to the rear wheel via a linkage affixed to the seat riser. In U.S. Pat. No. 1,047,431, a leaf spring arrangement connected at the bottom of the seat riser tube is intended to absorb shocks received at the rear wheel. In U.S. Pat. No. 1,056,492, a motorcycle frame is disclosed in which a shock absorber is included in the tubular arms 4. Still another approach is found in U.S. Pat. No. 1,148,170, in which a shock absorbing spring is located around the seat riser, and connected to a pivotable linkage at the top of the seat riser.
A more recent approach can be found in U.S. Pat. No. 3,865,402, in which a shock absorber is mounted on either side of the rear wheel similar to a conventional motorcycle suspension. In U.S. Pat. No. 3,931,990, a single shock absorber is positioned substantially horizontally between the seat riser and the downtube of the frame. The shock absorber is pivotably linked to the rear wheels at the seat riser. Yet another approach is shown in U.S. Pat. No. 3,982,770, in which a single shock absorber is located on a tube extending between the top of the down tube and the middle of the seat riser, and is thence connected to the rear wheel.
Finally, still another approach is shown in an advertisement for the "Descender" mountain bicycle, in which a single shock absorber is positioned in front of and pivotably connected to the seat riser tube, with the other end of the pivot arm connected to a rear wheel swing arm.
The difficulty with each of these prior art designs is that each of them absorbs a significant amount of force which would otherwise provide forward movement. While this loss is not significant for motorcycles, it is unacceptable where the only available motive force is the pedaling of a human being.
The energy loss in cycles found in the prior art results from the fact that when the rear sprocket on the cycle turns, the rotational force on the rear wheel causes the rear wheel to rise upward against the suspension. This will typically be perceived as the cycle settling slightly.
There has therefore been a need for a suspension bicycle which transforms substantially all of the pedaling force into forward motive force without substantial loss to the suspension.